July 12, 2016, marked a turning point in the long-standing disputes over the South China Sea. After more than three years of proceedings at the Permanent Court of Arbitration, an international body in The Hague, a tribunal constituted under the UN Convention on the Law of the Sea (UNCLOS) issued a widely anticipated decision in a case the Philippines brought in 2013 to challenge China’s maritime claims to most of the contested waterway.

Many observers had expected the tribunal to rule in Manila’s favor. They’d also expected China to reject the tribunal’s decision, since Beijing, a signatory to the convention, has long opposed the proceedings and had warned that it would not abide by the judgment. But few anticipated a ruling as definitive as the one ultimately handed down. The tribunal ruled in favor of the Philippines on almost every count, declaring nearly all of China’s maritime claims in the region invalid under international law.

In so doing, the tribunal has brought a substantial amount of new clarity to a number of contentious legal issues and has set precedents that will affect the law of the sea for years to come. But it has also created an immediate problem: China’s defeat was so crushing that it has left Beijing few ways to save face. Chinese officials may feel that the tribunal has backed them into a corner—and respond by lashing out. That’s especially problematic because international law has no simple enforcement mechanism, so if China decides to defy the tribunal, neither it, nor the Philippines, nor any other interested states will be able to do much to induce China to cooperate. Washington and its local partners can still avoid a dangerous escalation, but only if they encourage China to abide by the ruling while making clear to Beijing that it has not been trapped by it.

ERIK DE CASTRO / REUTERSA protest over the disputes in the South China Sea outside the Chinese consulate in Metro